Proposers to the observing call for NEID should use this calculator to estimate
the exposure times for their observations given a target SNR or RV precision,
and the inverse of those functions. This exposure time calculator was written
by the NEID Science Team and is based on initial best-estimates for the total
system throughput as a function of wavelength, precision from the default data
pipeline, and based on template stellar spectra at vsini = 2 km/s and solar
metallicity. All throughput estimates are deliberately conservative, and there
is an additional 30% margin built-in on top of this conservatism.
This calculator will be updated as better estimates of system performance
become available, and as on-sky performance is measured.
About the NEID Exposure Time Calculator
This calculator is based on precomputed grids with parameter bounds of:
2700 K < Teff < 6600 K
3 < V-mag < 17
10 s < exptime < 3600 s
0.3" < seeing < 1.9" s
Interpolating beyond these bounds will result in errors in the returned RV values.
All calculations are based on BT-Settl synthetic stellar spectra (with
logg = 4.5 and solar metallicity), available at:
http://phoenix.astro.physik.uni-goettingen.de/?page_id=15
The grids use a NEID throughput model with R ~ 95,000 and 380 nm -
930 nm spectral coverage and a median KPNO atmospheric transmission curve.
The calculator assumes airmass 1.1.
For RV precision estimates, we exclude regions of the spectrum with 1% or
deeper telluric features (based on TelFit model for WIYN observatory).
Median WIYN seeing is 0.8".
SNR is reported per 1D extracted pixel. The NEID resolution element is approximately
5 pixels wide.
Note that this exposure time calculator reports only the photon noise contribution to the RV precision. This contribution must be added in quadrature to the 27 cm/s instrumental floor to determine the total measurement precision.
NEID
A python implementation of the NEID Exposure Time Calculator is available here. (https://bitbucket.org/erik_timmermann_noao/neid-etc)